This invention relates to a polishing tool, and more particularly to a polishing tool used for a Chemical-Mechanical Planarization (CMP) process.
With the miniaturization trend of semiconductor elements, the control in the manufacturing process of semiconductors is more and more important. As for the planarization process, the traditional Spin-on Glass and Etch Back are hard to meet the current requirement of planarization, and Chemical-Mechanical Planarization (CMP) are being employed with increasing frequency.
The application of fixed abrasive pads is so far the most advanced technology in CMP to achieve global planarization. The fixed abrasive pad is patented by the 3M company for their micro-replication technology. By mixing the CeO2 abrasive particles with resin so as to form protrusions on the surface, the fixed abrasive pad is capable of removing the material on the xe2x80x9cupxe2x80x9d area of the wafer topography without touching the xe2x80x9cdownxe2x80x9d area of the wafer topography (i.e. IC). In addition, KOH is usually added on the pad for preventing the wafer surface from being adhered with silicon oxide and CeO2 residues to reduce the formation of scratches and increase the polishing rate. Since the liquid slurry is not used for this type of pad, it is often referred as xe2x80x9cslurry-freexe2x80x9d CMP.
The fixed abrasive pad is usually combined with non-rotary polishing tool (such as stationary magazine web and high speed linear belt) to polish the wafer. The traditional rotary polishing tool is not suitable for the fixed abrasive pad due to the following disadvantages:
1. The lifetime of the pad is short due to the repetitive wearing of the pad in the same area and thereby increasing the production cost.
2. The released CeO2 powder and fragments remain on the pad and tend to agglomerate, and further cause scratches on the wafer surface.
3. The wafer edge uniformity is difficult to control, since the advanced carriers are all designed with edge ring pressed on the pad, which is still not yet proven for the fixed abrasive pad.
The polishing tool with a wafer sitting on the vacuum chuck and a small polishing pad above moving across the wafer surface is already available (as disclosed in U.S. Pat. No. 6,227,956), but all are designed for conventional consumables. This type of polishing tool used for the conventional consumables has the following disadvantages:
1. The wafer still rotate at high speed which causes large amount of slurry consumption due to the strong centrifugal force.
2. The friction force between the wafer and the pad is large so that the polishing head is hard to move.
3. The uniformity control is difficult due to the interaction between process parameters and slurry flow patterns under the pad.
Therefore, the present invention provides a polishing tool to overcome the disadvantages of the prior art described above.
It is an object of the present invention to provide a polishing tool used for a CMP process.
In accordance with an aspect of the present invention, the polishing tool includes a polishing platen for holding a wafer faced-up thereon and carrying the wafer to move to and fro between a first position and a second position, a polishing pad for polishing the wafer, and a holder for holding the polishing pad to self-rotate and carrying the polishing pad to move across the wafer surface and further driving the polishing pad to polish the wafer.
Preferably, the size of the pad is smaller than that of the wafer.
Preferably, the diameter of the polishing platen is ranged from 12 to 20 inches.
Preferably, the distance between the first position and the second position is at least one diameter of the wafer.
Preferably, the distance between the first position and the second position is 2 times the diameter of the wafer
Preferably, the moving rate of the polishing platen is ranged from 1 to 1000 mm/sec.
Preferably, the moving rate of the polishing platen is 1 m/min.
Preferably, the movement of the polishing platen with the wafer between the first position and the second position is linear.
Preferably, the polishing platen is a vacuum chuck.
Preferably, the vacuum chuck has plural air-extracting holes, which are vacuumed after the interior air thereof is extracted, for allowing the wafer to adhere tightly to the vacuum chuck.
Preferably, the plural air-extracting holes are arranged as a plurality of rings with different diameters and are air-extracted adjustably for corresponding to the size of the wafer.
Preferably, the polishing pad is a fixed abrasive pad.
Preferably, the diameter of the polishing pad is ranged from 1 to 12 inches.
Preferably, the polishing tool employs KOH solution for preventing the wafer surface from being adhered with powder and fragments generated in the polishing process.
Preferably, the KOH solution is injected into the polishing tool through the holder.
Preferably, the KOH solution is supplied directly on the wafer surface.
Preferably, the self-rotate speed of the pad is between 1xcx9c1000 RPM.
Preferably, the holder is interchangeable for handling the polishing pad with different size.
Preferably, the polishing tool further includes a movable arm connected with the holder for carrying the polishing pad to move across the wafer surface.
Preferably, the moving path of the polishing pad to move across the wafer surface is a substantial curve
The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: